The 36-year-old wore a Willow white gown that pushed up her bust and had triangle panels slashed into it, revealing her bare midriff.
But the actress who walked the red carpet with her husband, actor Sacha Baron Cohen, appeared to be feeling the effects of the Arctic conditions that have hit London, as she quickly had her gallant husband take off his jacket and wrap it around her before making it into the movie theatre.
Sacha, who plays Monsieur Thénardier in the movie, was joined on the red carpet by co-stars Hugh Jackman, Russell Crowe, Eddie Redmayne, Anne Hathaway, Helena Bonham Carter and Amanda Seyfried, who gave Isla a run for her money in a plunging black Balenciaga number.
The movie’s star Anne Hathaway, who dropped two stone for the role and chopped her hair, wore a backless white beaded couture gown by Givenchy.
Tipped for an Oscar for her role, she said being cast as tragic heroine Fantine in the film adaptation of the musical was her "dream" job, as she attended the movie's world premiere.
. Asked if she would have gone beyond the drastic lengths of cutting her hair and slimming down to play her emaciated character, Hathaway added: "I didn't have to pull out my teeth, but no one asked, so yes, I would do anything."
The star was joined by director Tom Hooper and co-stars Hugh Jackman, Russell Crowe, Amanda Seyfried and Eddie Redmayne on the red carpet.
The film also stars Helena Bonham Carter and Sacha Baron-Cohen and will hit screens on January 11.